Some of these on both cassette and turntable had built in speed control.
Very non sophisticated and seems mainly to be of two main types. The cheap
and nasty ones use an old fashioned governor that disconnects power when a
certain speed is reached. These tend to generate a lotof interference.
The second sort have a little pcb in the back end of the motor that somehow
monitors current anbut not actual speed. I did read these worked from some
kind of clever back emf action, but they were not mega stable over time as
no true servo control was used.


Brian

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This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"News" wrote in message
...

Just been dismantling an old and very dead Ferguson music centre, probably
from the 70s. Nice little DC motor that powered the turntable, for which
I have another use in mind.

Using a bench power supply, the motor spins well at 5v, but I don't know
the voltage the motor was designed for, there being nothing stamped or
marked on it. Were these things fairly standard, and is 12v likely to be
the maximum voltage, or is that 'how long is a piece of string' ?
--
Graeme